Run 2 mongodb updates in 1 query based on a field value

Question

I need to update a record in mongodb where the new value depends on the value of another field in the record.

For instance given the following collection

{id: 1, list: []}
{id: 2, list: [6]}
{id: 3, list: []}
{id: 4, list: [6]}
{id: 5, list: []}

I want to be able to say:

if ('id' is in [1, 3, 5]) => add the value '6' to 'list'
else => remove the value '6' from 'list'

The outcome would be:

{id: 1, list: [6]}
{id: 2, list: []}
{id: 3, list: [6]}
{id: 4, list: []}
{id: 5, list: [6]}

This could be done in 2 update queries, as follows, but I am trying to do it in 1:

db.collection.update({$in: [1, 3, 5]}, {$addToSet: {list: 6}})
db.collection.update({$in: [2, 4]}, {$pull: {list: 6}})

The code is in Java.

score 1 · Accepted Answer · answered Dec 12 '12 at 22:06

1

MongoDB does not have a internal case statement as of yet which would allow you to perform this like in SQLs own case abilities.

As such you will need to do each separately, however you can change your latter query to be more along the lines of:

db.collection.update({$nin: [1, 3, 5]}, {$pull: {list: 6}})

That should accomplish the if statement you provided better.

answered Dec 12 '12 at 22:06

Sammaye

The only reason I had {$in: [2, 4] is that [2, 4] is not necessarily the complement of [1, 3, 5]. it could be just [2]. – ben39 Dec 13 '12 at 03:30
it is always good NOT to use $nin or any negate operator if possible. – Raxit Sheth Dec 13 '12 at 05:13
1

@RaxitSheth It is fine to use a negation property provided you are not negating a boolean or a low selectivity field which he is not, negation operators can still use a covered index. – Sammaye Dec 13 '12 at 08:09
@Sammaye interesting! Tnx – Raxit Sheth Dec 15 '12 at 07:24

1 Answers1